Chemical vapor deposition reactor

ABSTRACT

A CVD reactor, such as a MOCVD reactor conducting metalorganic chemical vapor deposition of epitaxial layers, is provided. The CVD or MOCVD reactor generally comprises a flow flange assembly, adjustable proportional flow injector assembly, a chamber assembly, and a multi-segment center rotation shaft. The reactor provides a novel geometry to specific components that function to reduce the gas usage while also improving the performance of the deposition.

CROSS REFERENCE TO RELATED APPLICATION

This is a divisional patent application of U.S. Ser. No. 12/248,167,filed on Oct. 9, 2008 which claims the benefit of U.S. ProvisionalApplication No. 60/979,181, filed Oct. 11, 2007, the entirety of whichis hereby incorporated by reference into this application.

FIELD OF THE INVENTION

The invention pertains to chemical vapor deposition (“CVD”) reactors,including metalorganic chemical vapor deposition (“MOCVD”) reactors.Description of the Related Art

Chemical vapor deposition (“CVD”) reactors, and in particularmetalorganic chemical vapor deposition (“MOCVD”) reactors are used todeposit solid material layers onto a wafer. Such materials typicallyinclude compounds of the group III column and group V column elements ofthe periodic table (referred to as III-V material, but also include“II-VI materials” as well). Materials such as silicon (Si), siliconcarbide (SiC), zinc oxide (ZnO) and others are also deposited on wafersor other surfaces using these reactors. Commercially, these reactors areused in the manufacture of solid-state (semiconductor) microelectronicdevices, optical devices and photovoltaic (solar) devices, and otherelectronic/opto-electronic materials and devices.

In operation, typically a flat-cylindrical wafer carrier with one ormore wafers loaded in shallow pockets on the upper surface of the wafercarrier is heated to the required temperature (450-1400° C.) by a heaterassembly located (typically) below the lower surface.

A continuously-supplied gas mixture is directed to flow over the surfaceof the heated wafer carrier and wafers. The gas mixture is predominantly(about 75-95%) a carrier gas, which is an appropriate inert gas(typically hydrogen or nitrogen) that functions to define the generalflow pattern in the reactor and to appropriately dilute the reactantgases. The remainder of the gas mixture is comprised of group V reactantgases (about 4-23%), group III reactant vapors (about 1-2%), and dopantgases or vapors (trace levels).

The group V gases decompose immediately above and on the surface of theheated wafer carrier and wafers, allowing atoms of the central group Velement to incorporate into the material layer being deposited (both onthe wafers and on the surface of the wafer carrier). The group III gasessimilarly decompose to provide atoms of the group III element. Thedopant gases similarly decompose to provide atoms which function toalter the electrical conductivity characteristics of the semiconductormaterial.

After flowing radially outward over the surface of the wafer carrier andwafers, the gas mixture (now also containing reactant by-products) exitsthe reactor through one or more exhaust ports. A vacuum pump istypically used to draw the gas mixture through the reactor, particularlybecause most materials deposit optimally at pressures lower thanatmospheric pressure. After passing over the heated wafer carrier, thegas mixture begins to cool rapidly, which results in rapid condensationof byproducts into the solid state. These tend to coat the interiorsurfaces of the reactor chamber (below the wafer carrier) and exhausttubing.

The wafer carrier is typically rotated from 100 to over 1000 RPM to aidin uniformly distributing the flowing gas mixture, and to reduce thethickness of the mass-transport boundary layer, which increases theefficiency of reactant usage as well as byproduct removal.

Material is deposited using this method in batches. The reactants arenot supplied continuously during the batch run. The typical batch run isconducted as follows. During the initial stage of the run, only thecarrier gas is supplied at a low flowrate. Then, in unison, the wafercarrier rotation is gradually increased to the desired value, the wafercarrier temperature is increased to the desired value, and the carriergas flowrate is increased to the desired value. The group V reactant gasis typically switched into the reactor first (at a specific temperaturelevel) to stabilize the surface of the substrate wafers (preventdesorption of group V atoms), and then the group III and dopant gasesare switched in to effect “growth” of material layers (material growthonly occurs when at least one group V and at least one group III sourceare switched to the reactor). Brief pauses where no group III or dopantgases are supplied to the reactor may occur, but at least one group Vgas is typically supplied during the entire growth stage (whiletemperature is above about 350-400° C.).

Once all material layers have been grown, the temperature is graduallydecreased. Once the temperature is below about 350° C., the group Vreactant gas is switched off, and the rotation, temperature and carriergas flowrate are decreased to the starting levels. The wafers are thenremoved from the wafer carrier, either by opening the reactor chambertop or by transfer of the entire wafer carrier out of the reactorchamber by mechanical means. Depending on the material being deposited,the same wafer carrier may be used for many batch runs, or for only onerun, before the excess material deposited on the exposed top surfacemust be cleaned off.

There are a number of known MOCVD reactor systems used in the marketcurrently. Each of these known MOCVD reactors suffers from deficienciesand disadvantages.

One design uses a tall cylindrical vessel with a gas flow injection toplid that attempts to spread flow evenly over the entire lid area. To alimited extent, the vertical separation prevents byproduct materialdeposition on the internal lid surface through which the gas flowsenter. The lid design, however, has disadvantages that include:ineffective isolation of the multiple gas spreading “zones” in the lid,resulting in pre-reaction and byproduct material deposition; ineffectivespreading of gas flows over the large zone areas from supply gas tubes,resulting in non-optimal material characteristics as well as additionalmaterial deposition on the internal lid surface; and the high flowratesof gas required to produce a relatively uniform outlet flow from the lidthrough the large chamber volume.

A second design uses a short cylindrical vessel with a gas flowinjection top lid that is closely spaced to the (heated) depositionsurface. The close spacing is effective in minimizing the reactor volumeand providing effective contacting of the gas to the deposition surface,and the gas chamber isolation is effective. However, the close spacingresults in byproduct material deposition on the internal lid surface andrequires cleaning after nearly every process run, which requires greatermaintenance time and costs and less productive time. In addition to highmaintenance costs, the cost to manufacture the top lid is very high dueto the complexity of the lid and the large area.

Both designs are expensive to use. The first design has a very highoperating cost and produces a product of lower quality and performance.The second design has a relatively lower operating cost, but highersystem maintenance requirements.

A CVD reactor system that has a lower production price and operatingcosts is desirable. A CVD reactor system with improved characteristicsof deposited material, high uptime and high quality is desirable.

SUMMARY OF THE INVENTION

A CVD reactor, such as a MOCVD reactor conducting metalorganic chemicalvapor deposition of epitaxial layers, is provided. The CVD or MOCVDreactor generally comprises one or more of a flow flange assembly,adjustable proportional flow injector assembly, a chamber assembly, anda multi-segment center rotation shaft.

The CVD reactor provides a novel geometry to specific components thatfunction to reduce the gas usage while also improving the performance ofthe deposition. In one aspect, a number of CVD reactor components withnovel geometries are described. In another aspect, new components aredescribed that address the problems of conventional CVD reactors. Forexample, the chamber top and side wall has a geometry that issignificantly different from conventional components. The top and sidewalls form a flared or curved conical surface. The exit region of thereactor also has an improved geometry that includes a tapered or slopedsurface. A novel gas injector is included in one embodiment of theinvention to further improve on performance and economy.

The inventive design provides a number of advantages. The CVD reactorreduces the volume of the reactor, provides a flow-guiding surface whichdirects entering gas flows to intimately contact a deposition surface,provides an additional flow-guiding surface to prevent back-entry ofspent reaction gas into the main reaction volume, provides highlyuniform fluid cooling or temperature control of key internal reactorsurface, and provides means of reducing heat losses from the depositionsurface.

The reactor design addresses a number of the problems with existingdesigns including but not limited to the following: (1) high/inefficientgas and chemicals usage, (2) non-uniform distribution of entering gasflows, (3) high manufacturing costs of equipment, and (4) deposition ofproblematic byproduct materials on internal reactor surfaces. The resultis advantages of lower operating cost, improved characteristics ofdeposited material layers, and lower machine maintenance requirements.

The flow flange assembly comprises a three-dimensional tapered or flaredcone upper surface and thin fluid gap immediately behind the surface, incontrast to vertical cylindrical walls of other designs. The designreduces reactor volume and gas usage, effectively guides gas towardsdeposition surface for more efficient chemicals usage, and provides forapproximately uniform radial velocity for improved depositionuniformity.

The adjustable proportional flow injector has several features includingsmaller area than deposition surface, isolated flow zones, a singleadjustable flow zone with no separation barriers, and uniform coolingfluid flow profile. These features address several problems in prior artinjectors by providing a lower gas flowrate, lower manufacturing cost,no zone cross leak and resulting pre-reaction and by-product materialdeposition, and improved uniformity of deposited material.

In one embodiment, the adjustable proportional flow injector assemblycomprises one or more gas chambers for separately maintaining one ormore reactant gas flows and a fluid cavity for regulation of gastemperature prior to injection of the gas into the reactor chamber. Theadjustable proportional flow injector assembly receives one or more gasinlet streams from supply tubes and spreads/diffuses these flows for auniform outlet flow velocity, while keeping the gas streams separateduntil they exit, and also regulating the temperature of the gas as thegas exits the adjustable proportional flow injector assembly.

In one embodiment, the chamber assembly generally comprises a conical orsloped lower flow guide. The lower flow guide prevents gas recirculationback into the reaction zone, improves smoothness of flow from the outeredge of the wafer carrier into the exhaust ports for a more stableoverall reactor flow profile, reduces heat losses at the outer edge ofthe wafer carrier for better temperature uniformity and improvedmaterial characteristics.

An embodiment of the wafer carrier has a cylindrical plate made of hightemperature resistant material that holds the substrate wafer(s) withinthe reactor volume, and, in embodiments of the invention, transfers heatreceived from the heater assembly to the wafers. The center rotationshaft is generally in communication with the wafer carrier and causesrotational movement of the wafer carrier. In an embodiment, the centerrotation shaft penetrates through the base plate center axis, usually incombination with a rotary vacuum feedthrough (such as a ferrofluidsealed type), and supports and rotates the wafer carrier within thereactor.

In a particular embodiment, the reactor comprises a two-piece wafercarrier having a top and a bottom, the top having properties optimal forholding substrate wafers and the bottom having properties optimal forheat absorption.

A multi-segment center rotation shaft is provided in one embodiment. Themulti-segment shaft has two or more segments that may optionally be usedin the reactor. At least one segment of the multi-segment shaft is madefrom a material having a low thermal conductivity. The multi-segmentshaft may have segment interfaces designed to have a high thermaltransfer resistance, to reduce thermal losses from the wafer carrier.The multi-segment shaft may generate additional heat near the center ofthe wafer carrier and provide a thermal barrier to heat losses from thewater carrier and/or shaft.

BRIEF DESCRIPTION OF THE DRAWINGS

The following is a general description of the drawings filed herewith.

FIG. 1 is a perspective view of one embodiment of the entire reactorchamber assembly.

FIG. 2 is a side view of one embodiment of the entire reactor chamberassembly.

FIGS. 3-5 show cross-sectional views of one embodiment of the entirereactor chamber assembly.

FIG. 6 shows a perspective view of one embodiment of the flow flangeassembly.

FIG. 7 shows an exploded side view of one embodiment of the flow flangeassembly.

FIG. 8 shows an exploded underside view of an embodiment of flow flangeassembly.

FIGS. 9A-9C show three cross-sectional side views of an embodiment ofthe upper flow guide.

FIG. 10 shows a close up cross sectional view of an embodiment of theupper flow guide.

FIG. 11 shows a side view of an embodiment of the adjustableproportional flow injector assembly.

FIG. 12 shows an exploded side view of an embodiment of the adjustableproportional flow injector assembly.

FIGS. 13-15 show three cross-sectional views of an embodiment of theadjustable proportional flow injector assembly.

FIGS. 16A and 16B show a top interior view of an embodiment of theadjustable proportional flow injector gas chamber machining.

FIGS. 17A and 17B show a bottom view of an embodiment of the adjustableproportional flow injector assembly.

FIG. 18 shows a close up cross-sectional view of the dual o-ring seal ofthe adjustable proportional flow injector assembly sealed to a flowflange assembly.

FIG. 19 shows a perspective view of an embodiment of the chamberassembly.

FIG. 20 shows a top view of an embodiment of the chamber assembly.

FIGS. 21A and 21B show two exploded views of an embodiment of the centerrotation shaft assembly.

FIG. 22 shows a side view of an embodiment of the center rotation shaftassembly.

FIG. 23 shows a cross-sectional view of an embodiment of the centerrotation shaft assembly.

FIG. 24 shows a close up cross-sectional view of an embodiment of thecenter rotation shaft assembly.

FIGS. 25A-25C show an alternate embodiment of subassemblies of the gaschambers of the adjustable proportional flow injector assembly.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described in detail using preferredembodiments. The present invention, however, is not limited to theseembodiments. Additionally, a requirement in an embodiment is freelyapplicable to other embodiments, and requirements are mutuallyreplaceable unless special conditions are attached. Specifically, a CVDreactor or MOCVD reactor, and components and parts of the reactors, aredescribed in further detail below. The CVD reactors or MOCVD reactorsmay comprise other components and parts which are not specificallymentioned herein. Further, it should be understood that the scope of theinvention pertains to CVD reactors or MOCVD reactors which may comprisesome of the components and parts discussed herein or may comprise all ofthe components and parts discussed herein.

FIG. 1 illustrates a front perspective view of one embodiment of theentire reactor assembly 1. The entire reactor assembly 1 is comprised ofthree subassemblies that together form the entire reactor assembly 1.The three subassemblies are the flow flange assembly 3, the adjustableproportional flow injector assembly 5, and the chamber assembly 7. FIG.2 illustrates a side view of the reactor assembly 1 as well as some ofthe individual components that are visible from the exterior of thereactor 1. Those components are discussed in more detail below.

FIGS. 3-5 illustrate a cross sectional view of the entire reactorassembly 1 showing the interconnection of the three subassemblies, and across-sectional view of the individual components that make up the threesubassemblies. As in FIGS. 1 and 2, the flow flange assembly 3, theadjustable proportional flow injector assembly 5 and the chamberassembly 7 are illustrated. The individual components of the threesubassemblies 3, 5, and 7 are also indicated and discussed in greaterdetail below.

FIGS. 6-10 and 18 show several views of one embodiment of flow flangeassembly 3. The flow flange assembly 3 comprises a main flange body 30and has an upper opening 31 which defines a mating port for the flowinjector assembly 5 on the top and mates to the chamber assembly 7 onthe bottom end (shown best in the cross section view of FIGS. 3-5.) Theflow flange assembly 3 has an upper flow guide 32, which, along with theflow injector and wafer carrier, defines the reactor volume 33 and thegas flow profile within the reactor volume, fitted within the mainflange body 30.

The upper flow guide 32 preferably has a three-dimensional tapered coneoutward facing surface 34 (as opposed to vertical cylindrical walls ofprior art designs). The upper flow guide 32 is positioned and fitswithin the main flange body 30 (as best shown in FIGS. 7 and 8. Theunderside 35 of the main flange body 30 has a corresponding shape toreceive the inward facing surface 36 of the upper flow guide 32 so thata thin fluid gap or cavity 37 is formed immediately behind the upperflow guide 32, between the upper flow guide 32 and the main flange body30 (best illustrated in FIGS. 8-10). In an embodiment, such as depictedin the FIGS. 9 a-c, fluid cavity collection channels 41, 42 (two pointshere connect with the thin fluid cavity 37 through flow orifices 40.

The geometry of the upper flow guide 32 minimizes reactor chambervolume, suppresses recirculation eddies within the reactor chambervolume 33 and provides for efficient contacting of the reactant gas withthe wafer carrier surface 77.

In one embodiment, as best shown in FIGS. 3-5 the upper flow guide 32has a first (upper) diameter D-1 substantially equal to the diameter ofthe adjustable proportional flow injector (APFI) 7 and second (lower)diameter D-2 substantially equal to the diameter d3 of the wafer carrier76 (as shown in FIG. 20). As illustrated in the figures, the firstdiameter D-1 is smaller than the second diameter D-2. The first diameterD-1 preferably is from about 0.2 to 0.5 of the second diameter D-2. Theupper flow guide 32 is not strictly conical shaped, but rather curved asthe guide extends downward and flares out as it approaches D-2. Theupper flow guide 32 creates a gas flow pattern where a uniformlydistributed, downward-flowing gas stream is directed towards the wafercarrier 76, but the gas stream is also turned laterally and expanded, sothat a smaller diameter flow injector 5 can be used to uniformlydistribute flow over a substantially larger wafer carrier 76, withoutthe occurrence of recirculation of gas within the reactor chamber volume33.

The curved or flared profile of the upper flow guide 32 providesapproximately equal radial gas velocity. An upper flow guide 32 withthis geometry is alternately referred as an expanding cone upper flowguide 32. While not bound by theory, for a gas flow moving radiallyoutward, the gas must cross a continuously increasing cross sectionalarea (which increases with radius for cylindrical geometries), and as aresult, the flow velocity must decrease. In order to maintain asubstantially constant velocity, the height H-1 of the containinggeometry may be gradually reduced, so that the cross sectional area(product of circumference multiplied by height) remains substantiallyconstant, which counteracts the increase of the circumference withradius.

The flow flange assembly 3 preferably has a fluid gap 37 positioneddirectly behind the upper flow guide 32 (between the upper flow guide 32and the main flange body 30). In embodiments of the invention, the fluidgap 37 is relatively thin (about 0.1 inches or less) which, for fluidflow rates of approximately 1 gallon per minute and for fluids havingdensity and viscosity values within an order of magnitude of water, willresult in a Reynold's number value of less than 3200, which isindicative of laminar flow within the fluid gap and efficient usage offluid. This configuration results in reduced usage of fluid and/orreduces the capacity of a fluid recirculator (if areservoir/recirculator heat exchanger system is to be employed).

The flow flange assembly 3 may further comprise bottom/outer totop/inner flow through the fluid gap 37 for air removal and counter-flowheat exchange. That is, fluid flows in a reverse direction through thefluid gap from the direction the gas is flowing in the reactor volume.This type of flow path through the fluid gap is achieved in oneembodiment from a supply channel 41, optionally down through one or moresupply conduits (not shown). Each supply channel 41 has one or more flowrestricting orifices 40 proximate to the end of each supply channel 41.The flow restrictive orifices 40 sufficiently restrict the flow suchthat an equal flow rate of fluid passes through each supply channel,immediately prior to entering the fluid gap 37, producing a uniform flowdelivery around the outer circumference of the fluid gap 37. Fluid flowsradially inward though the fluid gap 37, and then passes through asecond set of flow restricting orifices 40 within that transfers thefluid to a return channel 42 (optionally via one or more return conduits(not shown). Fluid is supplied via supply channel inlet tube 45 andreturned through a fluid outlet tube 46. The flow characteristics of thefluid within the fluid gap 37 result in improved temperature uniformitywithin the reactor chamber volume 33, which improves the uniformity ofthe gas flow profile and deposition uniformity. The bottom/outer totop/inner flow pattern in the fluid gap 37 results in counter-flow heatexchange and effective removal of air from the gap 37.

A gap 43 between upper flow guide 32 at the outermost diameter of theupper flow guide D-2 (i.e. at the end of the upper flow guide proximateto the wafer carrier 76) and wafer carrier upper surface 77 at theoutermost diameter d3 of the wafer carrier 76 generally inhibits orprevents recirculation of ejected gas above the wafer carrier 76. Asshown particularly in FIGS. 3-5, the wafer carrier 76 rests on the topof a center rotation shaft 75. The upper flow guide 32 outer diameterD-2 is about equal to that of the wafer carrier d3 where the upper flowguide 32 is closest to the wafer carrier 76. At this point, theseparation between these two parts H-2 is at a minimum value and the gap43 facilitates the inhibition or prohibition of recirculation of theejected gas within the reactor chamber volume 33. For example, the gapmay have a dimension H-2 of about 1.00 inch or less, such as about 0.25inch or less. The gas flowing downward from the adjustable proportionalflow injector assembly 5 turns laterally within the reactor chambervolume 33 and flows radially outward. When it reaches the gap 43, thegas achieves a maximum flow velocity, and once past the gap 43, the gasbegins to expand and decelerate in an exhaust collection zone 44 that isproximate to the gap 43, thereby preventing backward recirculation ofthe spent gas mixture, (i.e. the gas which has moved away from thereaction area at and above the wafer carrier 76).

In a preferred embodiment of the invention, the reactor 1 with anexpanding cone upper flow guide 32 also incorporates a lower flow guide72 (discussed in more detail below). The lower flow guide 72 preventsgas recirculation back into the reaction zone, improves smoothness offlow from outer edge of wafer carrier into exhaust ports for more stableoverall reactor flow profile, and reduces heat losses at outer edge ofwafer carrier 76 for better temperature uniformity and improved materialcharacteristics.

The adjustable proportional flow injector assembly 5 (hereinafter “APFI5”) in an embodiment of the invention is shown particularly in FIGS.11-18 and 25. The adjustable proportional flow injection is a flowinjector that receives multiple gas inlet streams from supply tubes andspreads or diffuses these flows for a uniform outlet flow velocity,while keeping the gas streams separated until they exit. Optionally theAPFI 5 also regulates the temperature of the gases as they exit theadjustable proportional flow injector. The APFI 5 is typicallycylindrical in shape (circular area and vertical height) and fits withinthe flow flange assembly 3. A cylindrical APFI is shown in the figureshowever, the APFI can be made in any shape and the exact shape willgenerally be dictated by the shape (area) of the upper opening 31 intowhich it is being mated. For example, if the upper opening 31 has asquare or rectangular shape, then the APFI will have a correspondingsquare or rectangular shape so that it can be mated.

The adjustable proportional flow injector assembly 5 generally comprisesa support flange 51, which provides structural integrity for thecomponents mated to the support flange 51 and gas chamber inlet tubes orports 54 that penetrate through the support flange 51. The supportflange 51 further provides for mating the entire adjustable proportionalflow injector assembly 5 to a main flange body 30.

The APFI 5 includes one or more gas chambers 52. In an embodiment, oneor more of the gas chambers 50 may be machined into a gas chambermachining 52 and are formed from a plurality of gas chamber top walls orsurface 57 and gas chamber bottom walls or surface 58. The gas chambertop wall 57 can be machined to form different zones as illustrated inthe top views FIGS. 16 and 17. The gas chambers 50 are separated fromthe other gas chambers 50 by gas chamber vertical walls 59 that extendfrom the gas chamber top walls 57 to the gas chamber bottom walls 58thereby forming the gas chambers 50. The one or more gas inlets 54,which may be incorporated into the gas chamber top walls 57, deliver gasto the one or more gas chambers 50 of the adjustable proportional flowinjector 5, such as in a vertical direction (i.e. about perpendicular tothe gas chamber top walls 57 and gas chamber bottom walls 58).

Each gas chamber 50 may receive a different gas stream and one or moreof these gas chambers may spread or diffuse the gas and keep a first gasstream separate from other gas streams or each gas stream separate fromanother, and create a uniform flow velocity over a specific outletsurface area. Additionally, each gas chamber 50 may be configured in thesame shape or different shape as the other gas chambers 50.

For example, as shown in FIG. 16 (the support flange 51 is removed fromthe figure) there is an outer gas chamber 50 a, and four intermediategas chambers 50 b and 50 c, and an inner gas chamber 50 d. In oneembodiment, the gas chamber 50 b receives Group III reactants andintermediate gas chambers 50 c receive group V reactants. The chambers50 a-d are separated by the vertical walls 59, the gas chamber top walls57 (not shown) and the gas chamber bottom walls 58.

The APFI 5 may also include a fluid cavity 60, which is located belowthe one or more gas chambers 50. The fluid cavity 60 may be formed bythe mating of a fluid cavity machining 53 to the gas chamber machining52. FIG. 17 shows the bottom view of an embodiment of the adjustableproportional flow injector assembly 5, showing the bottom face of thefluid cavity machining 53. Gas chamber outlets 61 may extend orpenetrate from the bottom wall 58 of a gas chamber through the fluidcavity 60, such as through conduit tubes 63, into the reactor chambervolume 33. The conduit tubes 63 may have the same or different innerdiameters and same or different outer diameters. Penetration of theconduit tubes 63 through the fluid cavity 60 permits the regulation ofthe gas temperature prior to introduction of the gases into the reactorchamber volume 33 by the appropriate control of the temperature of thefluid flowing through the fluid cavity 60. The fluid cavity 60 has afluid cavity outlet 66 positioned at about the center of the fluidcavity 60 connected to a fluid cavity outlet tube 67. Additionally,fluid cavity inlets 68 are provided through fluid cavity inlet tubes 69towards the periphery of the fluid cavity 60.

In embodiments that contain a fluid cavity diffuser 65 (discussed inmore detail below), the fluid cavity outlet 68 is positioned inside thecircumference of the diffuser 65, while the fluid cavity inlets 68 arepositioned outside of the circumference of the diffuser 65.

The adjustable proportional flow injector assembly 5 may optionally haveone or more of the following features. In one embodiment, the gas outletapertures 61 are preferably a smaller size than the gas inlets 54 (forexample there may be from about 100 to about 10,000 gas outletapertures). The number of gas outlet apertures 61 and the insidediameter and length of the conduit tubes 63 extending through the fluidcavity 60 depends on the specific gas composition, flowrate, temperatureand pressure and are also limited by the total surface area of thebottom wall 58 of a gas chamber and by manufacturing capabilities andcosts, the difficulty and cost increasing as the outside and insidediameters of the conduit tubes 63 decreases and as the spacing ofadjacent gas outlet apertures 61 decreases. Generally, however, thetotal cross sectional area of all of the conduit tubes 63 is preferablya factor between 2 and 6 times larger than the cross sectional area ofthe gas inlet 54 to a given gas chamber. This arrangement accounts forthe greater wall surface area and corresponding fluid shear and pressuredrop of the smaller-diameter conduit tubes 63 compared to the gas inlet54, such that the pressure drop across the set of conduit tubes of agiven gas chamber (that is, the pressure drop from the gas chamber tothe reactor chamber volume 33) is preferably from several Torr toseveral tens of Torr.

The gas chamber upper walls 57 and gas chamber bottom walls maypreferably be substantially parallel. The upper walls/surface 57 of allgas chambers can be substantially co-planar they can alternatively be ondifferent planes. Similarly gas chamber bottom walls 58 of all gaschambers 50 can be co-planar or alternatively on different planes.

The adjustable proportional flow injector assembly 5 may optionallycomprise one or more intermediate diffusing baffle plates 55 between andsubstantially parallel to the gas chamber upper walls 57 and the gaschamber bottom walls 58. When an intermediate diffusing baffle plate 55is used, an upper gas chamber section 50 a and a lower gas chambersection 50 b is formed in the gas chamber 50 comprising the intermediatediffusing baffle plates 55. For example, the upper gas chamber section50 a may be defined, generally, by the gas chamber upper wall 57, anupper surface of the intermediate diffusing baffle plate 55 and any sidewall(s) 59 and the lower gas chamber section 50 b may be definedgenerally by the gas chamber lower wall 58, a lower surface of theintermediate diffusing baffle plate 55 and any side wall(s) 59.

Gas outlet apertures 61 of each gas chamber 50 are joined to outletconduits (preferably small diameter tubes) 63 penetrating through thefluid cavity 60 which may be attached to or otherwise joined to thefluid cavity machining 53 thereby forming a lower fluid cavity wallproximate to the lowermost side of which is a boundary surface of thereactor chamber volume 33. The outlet conduits 63 preferably have anaperture pattern matching that of the combined set of gas chamber outletapertures 61.

A further embodiment of the adjustable proportional flow injectorassembly 5 concerns a fluid temperature control zone with uniform,radial flow profile. Temperature regulating fluid, for example coolingfluid, flows into an outer distribution channel 62. In an embodiment ofthe invention, the fluid cavity 60 has a fluid cavity diffuser 65. Thefluid cavity diffuser 65 is preferably a thin, cylindrical sheet metalring having a height slightly larger than the height of the fluid cavity60 and is preferably as thin as possible. In the preferred embodiment,the cylindrical sheet metal ring inserts into opposing circular groovesin the bottom surface of the gas chamber machining 53 and the uppersurface of the fluid cavity machining 52, the sum of the depth of thesetwo grooves preferably being equal to the additional height of the flowdiffusing barrier over that of the fluid cavity, so that fluid deliveredto the fluid cavity 60 at multiple inlets 68 at the outermost peripheryof the fluid cavity must immediately move tangentially before flowingthrough a plurality of preferably equally spaced small apertures 64 inthe flow diffusing barrier 65, resulting in a uniform flow distributionfrom the outermost periphery of the fluid cavity 60 radially inwardtowards the single outlet 66 at the center outlet 66 of the fluid cavity60. The small apertures 64 act as flow restricting orifices, whichsufficiently restrict flow so as to result in an equal flow through eachaperture 64

FIG. 25( a-c) illustrates an alternate method of fabricating the APFI.Not all APFI components previously described are shown. In order toincrease the ease and efficiency of both the manufacture and testing ofthe APFI, components of the APFI can be assembled from interchangeablemodules or subassemblies. For example, gas outlet aperturesub-assemblies 150 can be constructed from an upper plate 151, a lowerplate 152, and multiple conduits 63. The upper plate 151 constitutes thebottom wall 58 of a gas chamber 50 described above. The lower plate 152constitutes a portion of the bottom wall 58 of the fluid cavitymachining 53 previously described.

In this embodiment, the gas chamber machining 52 is constructed toreceive multiple gas outlet aperture sub-assemblies 150, such that theupper surface 153 of the upper plate 151 mates flush to one or morelower surfaces 155 of gas chamber walls 59 previously described. Theseam between the upper plates 151 of adjacent gas outlet aperturesub-assemblies 150 falls along the centerline of a given lower surface155 of a gas chamber wall 59 so that a seal may be formed that preventsany leakage between the fluid cavity 63 thus formed and any gas chamber50.

In the embodiment shown in FIGS. 25( a-c), the seam between the lowerplates 152 of adjacent gas outlet aperture sub-assemblies 150 andbetween the lower plate 152 of a given gas outlet aperture sub-assembly150 and the lower fluid cavity wall 157 integral with that gas chambermachining 52 may be sealed to prevent any leakage between the fluidcavity 63 and the reactor chamber volume 33. In one embodiment, it maybe sealed in such a manner that the lower surface 154 of each gas outletaperture sub-assembly 150 is flush with the lower surface 154 of allother gas outlet aperture sub-assemblies 150 and the lower surface 156of the gas chamber machining, although this is not required. Fluid isthus delivered into the fluid cavity 63 through multiple fluid cavityinlets 68 and exits through one or more fluid cavity outlets 66, wherethe fluid cavity diffuser 65 (not shown) is positioned in a similarmanner as previously described.

A further embodiment of the invention concerns methods for creatingpatterns of substantially equally spaced gas outlets in one or moreradial patterns. In accordance with these methods, one or more patternsof circular holes are arranged such that the holes are equidistant fromeach other, such as in square or hexagonal patterns. For the radialzones comprising the adjustable proportional flow injector gas chambers,a method comprises distributing holes so that they are substantiallyequidistant from each other as well as area boundaries. This methodgenerally comprises the steps of (1) arranging a first set of holes on afirst line adjacent and parallel to a first radial area boundary, withequal spacing between these holes in a radial direction, (2) determiningthe angle, with vertex at the center axis of the machining, between afirst point on the first line at a first radial distance from the centeraxis and the corresponding second point on a second line adjacent andparallel to a second radial area boundary, (3) determining the length ofthe arc, with origin at the center of the gas chamber machining, betweena first hole at a given radius lying adjacent to the first radial areaboundary and the corresponding second hole at the same radius lyingadjacent to the second corresponding radial area boundary, (4) dividingthis arc length by the desired center-to-center hole spacing distanceand (5) rounding the resulting number to the nearest integer. Steps(2)-(5) are repeated for each hole comprising the set described in step(1). This method produces a hole pattern with equal separation betweenradial sets of holes, and nearly equal separation of holes within eachradial set of holes. This method is particularly useful for producingsubstantially equidistant sets of holes in circular or semi-circularpatterns over small areas, where irregularities in hole spacing are moresignificant than for patterns over large areas.

The reactors may also comprise a gas distribution zone havingadjustability with no zone separating barriers (such as illustrated inFIG. 17). In this embodiment, the reactors comprise two or more gasinlet tubes 54 and a plurality of outlet holes 61 that geometricallyfunction to produce an adjustable outlet flow pattern through theplurality of holes 61. While not bound by theory, by increasing ordecreasing the amount flow to one or more of the inlet tubes 54, withouthaving any discrete vertical separation wall 59 between any of the inlettubes 54, stagnation areas that would normally be produced by the areabelow the separation walls, which can have not outlet flow holes, areeliminated.

The adjustable proportional flow injector assembly 5 may furthercomprise one or more sealed chamber tops, such as one or more o-ringsealed chamber tops, for cleaning and/or baffle changes. In a preferredembodiment, the gas chamber machining 52 includes o-ring groovesmachined into the top surface of the vertical walls 59 separating thegas chambers, which eliminates the gas chamber zone upper walls 57. Thisis because an o-ring lying along the upper surface of the vertical wallscan seal directly to the lower surface of the support flange 51 or othersingle intermediate sealing surface (rather than a plurality of weldedsurfaces). This configuration allows the gas chambers to be opened andcleaned or inspected, as well as reducing the number of parts required.

In a further embodiment, the adjustable proportional flow injectorassembly 5 comprises a dual o-ring seal with vacuum barrier zone, bestillustrated in

FIG. 18. Dual o-ring seal produced by o-rings 91 in o-ring grooves 92 inthe gas chamber machining 52 and the fluid cavity machining 53. Oneo-ring 91 a is positioned between the gas chamber machining 52 and themain flange body 31. A second 91 b is positioned between the fluidcavity machining 53 and the main flange body 30. A vacuum cavity 93 iscreated between the APFI, the main flange body 31, and the o-rings 91. Adifferential seal vacuum port tube 94 is included in the main flangebody 31 to create and release the vacuum seal. This configurationpermits easy removal of the adjustable proportional flow injector 5while negating gas molecule permeation of the o-ring elastomer material,due to the significantly lower vacuum levels produced in the volume inbetween the two o-ring seals than on either side of each seal.

An embodiment of the chamber assembly 7 is shown in FIGS. 19-20 andFIGS. 3-5. The chamber assembly 7 has a reactor baseplate main body 70.The reactor baseplate main body is connected to a reactor jar top flange100 via a reactor jar wall 101. The reactor jar top flange 100 mateswith the main flange body 30 of the flow flange assembly 3. Thebaseplate main body 70 contains ports for a number of components usefulin CVD reactors such as a center rotation shaft 75 (discussed in moredetail below), base plate exhaust tubes 79; high current feedthrough 90;and rotary vacuum feedthrough housing 88.

The chamber assembly 7 has components typically found in a CVD reactorsuch as a heater assembly comprising a heat source and heat reflectingshields for heating the wafer carrier 76. In the embodiment shown, oneor more heating elements 83 are positioned under the wafer carrier 76and one or more heat shields 84 are positioned under the heatingelements 83. For example, the heat source may be a filament for radiantheating or a copper tube for inductive heating, preferably arranged in aconcentric circular pattern to match the circular area of the wafercarrier. Other types of heater assemblies may be used for heating thewafer carrier 76.

The chamber assembly 7 has a lower flow guide 72. The lower flow guide72 has a frustoconical shape. The conical shaped lower flow guide 74 hasan inner diameter d-1 and an outer diameter d-2. Preferably, the innerdiameter d-1 is slightly larger than outer diameter d3 of the wafercarrier 76, although the inner diameter d-1 can be approximately thesame, smaller or larger than the outer diameter d3 of the wafer carrier76. The lower flow guide 72 is aligned approximately with the topsurface 77 of wafer carrier 76. The outer diameter d-2 of the lower flowguide 72 is larger than the inner diameter d-1 creating a slopingsurface in the downward direction.

In the preferred embodiment, the inner diameter d-1 is slightly largerthan outer diameter d3 of the wafer carrier 76. The spacing between theinner diameter d-1 of the lower flow guide 72 and the outer diameter ofthe wafer carrier 76 forces the gas ejected from the gap 43 between thewafer carrier 76 and the upper flow guide 32 to expand gradually, andinhibits or prevents recirculation of the ejected gas below the outeredge of the wafer carrier 76. Preferably, the inner diameter d-1 of thelower flow guide and the outer diameter of the wafer carrier 76 are inclose proximity to provide a narrow lower flow guide gap between thetwo, as the narrower the lower flow guide gap the more efficientejection of the gas and greater the inhibition or prevention of therecirculation of gases within the reactor chamber volume 33. In apreferred embodiment, the lower flow guide 72 is fabricated fromgraphite.

The chamber assembly 7 may contain a lower flow guide reflector 74. Thelower flow guide reflector 74 is positioned within the lower flow guide72 and extending from the circumference of the wafer carrier 76 andangled in a downward direction. The reflector 74 is constructed of athin piece of metal, preferably molybdenum. The reflector 74 acts toreflects heat inward and helps keep the heat constant over the surfaceof the lower flow guide 72.

In an embodiment, the lower flow guide 72 may be constructed of one ormore sections or pieces, such as a two-piece lower flow guide 72. Due tothe close spacing between the lower flow guide 72 and the wafer carrier76, and due to the high temperature the wafer carrier 76 reaches duringprocessing, in an alternate embodiment, the lower flow guide 76 has afirst piece that is immediately adjacent to the wafer carrier 76fabricated from a material having a superior temperature tolerance andcoefficient of thermal expansion about equal to or similar to that ofthe wafer carrier 76 material (typically graphite, sapphire or arefractory metal), and a second piece fabricated from a material thatdoes not have such temperature tolerance or coefficient of thermalexpansion, such as a material that is less expensive and more easilyformed than the material that comprises the first piece. In a preferredembodiment, the first piece is fabricated from graphite to provide theappropriate temperature tolerance and coefficient of thermal expansionmatch with the wafer carrier material.

The lower flow guide 72 may be in part or wholly an extension of thewafer carrier 76 extending from the diameter d3 of the surface of thewafer carrier 76 that holds the wafer, i.e. an outer edge profile of thewafer carrier surface 77 that holds the wafers. In this embodiment, allor a portion of the lower flow guide 76 is an extension of the wafercarrier from the outer circumference of preferably the wafer carrier topsurface 77, or alternatively the lower surface 78, or at some pointalong the circumference in between. In a particular embodiment, thelower flow guide 72 has a first section which is an extension of thewafer carrier 76, such as within the first few centimeters from thenarrow gap 40 between the wafer carrier outer diameter 76 and the upperflow guide 72, and a second piece that is completely separate from thewafer carrier 76 and is formed as a separate piece adjacent to the firstpiece.

The wafer carrier 76 for the reactor 1 may be a conventional one piecestructure, however, embodiments having alternative structures are withinthe scope of the invention. For example, in an embodiment of theinvention, the reactor may comprise a two-piece wafer carrier 76comprising a removable top (i.e. platter or surface that holds thewafers) and a bottom. The removable top may be made from a number ofmaterials, preferably sapphire and bottom may comprise graphite and mayfurther comprise a means for heating, such as RF heated (for inductiveheating of bottom and conductive heating of removable top and any waferson the surface of the removable top). The two-piece wafer carrier canhave the removable top replaced when necessary while the bottom can bereused.

For example, in one embodiment a two-piece wafer carrier has a sapphireremovable top for holding the wafers and a graphite bottom that supportsthe sapphire removable top. The sapphire top is non-porous and will notdegrade, which occurs with surfaces conventionally used, such as SiCencapsulant. The sapphire removable top can also be cleaned morerigorously (such as a rapid wet chemical etch, which is not easilyperformed with the graphite wafer carriers). The graphite bottom pieceis a heat absorber for conductive heat transfer into the sapphireremovable top and the wafers on the surface of the removable top, suchas within wafer pockets that may be machined in an upper surface of theremovable top.

In a further embodiment, the wafer carrier 76 is integral with (i.e.machined directly into) a portion of the center rotation shaft 75, whichshaft 75 extends downward from the center of a bottom surface 78 of thewafer carrier 76. The center shaft 75 (alternatively, the centerrotation shaft 75) extends downward through a heating coil and iscomprised of a material suitable for heating, for example a materialsuitable for induction heating. This center rotation 75 shaft can beheated just as the main portion of the wafer carrier 76 is, and providesa thermal barrier to the conductive heat losses that may occur withconventional supporting spindle shafts.

The center rotation shaft 75 for the wafer carrier 76 may be aconventional one piece structure; however, embodiments havingalternative structures may be used. For example, in one embodiment asshown in FIGS. 21-24, a multi-segment shaft 75 for the rotating wafercarrier, i.e. a shaft comprising one or more segments made from the samematerial or different material is used. In multi-segment embodiments, atleast one segment will have a substantially lower thermal conductivitythan the remaining shaft segment(s) used. The multi-segment spindle isparticularly useful in conjunction with radiant heaters although theinvention is not necessarily limited in this regard.

In the embodiment shown in FIGS. 21-24, there are three segments. Ashaft upper segment 81 is directly in contact with the wafer carrier 76.The shaft upper segment 81 has a susceptor or flange 82 at the proximalend on which the bottom surface 78 of the wafer carrier 76 rests. Whenradiant heaters are used, the upper segment is preferably fabricatedfrom a material (such as alumina or sapphire) having a lower thermalconductivity than the one or more of the remaining segment(s) of themulti-segment shaft 75. This selection of material produces the highestpossible thermal transfer resistance. Segment interfaces between themulti-segment center shaft 75 and the wafer carrier 76 can be designedwith minimal surface to further enhance the thermal transfer resistance.These features improve the temperature uniformity near the center areaof the wafer carrier, as well as reduce energy losses in operation ofthe reactor.

Alternatively, when an inductive heater is used in the reactor, thesegment in contact with the wafer carrier (the shaft upper segment 81)extends downward through an inductive heating coil. In this instance,the upper segment 81 is made of a material suitable for inductiveheating. For example, when an inductive heater is used in the reactor,the upper segment 81 of the multi-segment center shaft 75 is preferablyconstructed of graphite.

In one embodiment, the multi-segment shaft 75 has a shaft lower segment85 is constructed of a material that does not readily heat inductively(such as sapphire). The shaft upper segment 81 and shaft lower segment85 are connected via a spacer 86 that is, preferably, constructed fromalumina. The interfaces between the three (or more) segments preferablyhave minimal surface contact area to produce the highest possiblethermal transfer resistance. The surface area may be reduced byincluding machined recesses 87 in the segments at the point of interface(shown in FIG. 24); to create thin rails 96 around the circumference ofthe ends of the segments. Contact between the segments only occurs atthe thin rails 96 as opposed to the entire area of the segment ends. Thesegments are preferably secured by way of vented head cap screws 97.

There will be various modifications, adjustments, and applications ofthe disclosed invention that will be apparent to those of skill in theart, and the present application is intended to cover such embodiments.Accordingly, while the present invention has been described in thecontext of certain preferred embodiments, it is intended that the fullscope of these be measured by reference to the scope of the followingclaims.

1-27. (canceled)
 28. A chemical vapor deposition reactor comprising: aflow flange assembly; a wafer carrier configured to support at least onesubstrate wafer; and a center rotation shaft for rotating the wafercarrier, wherein the center rotation shaft comprise an upper shaftsegment having a flange at a proximal end located adjacent to the wafercarrier, wherein a bottom surface of the wafer carrier rests on theflange of the upper shaft segment, and further wherein the upper shaftsegment is fabricated from a material adapted for induction heating. 29.The chemical vapor deposition reactor according to claim 28, wherein theflow flange assembly comprises an upper flow guide having a curved orflared profile.
 30. The chemical vapor deposition reactor according toclaim 28, further comprising a lower flow guide surrounding the wafercarrier, wherein the lower flow guide, generally, has a sloped shape, aconical shape or a frustoconical shape.
 31. The chemical vapordeposition reactor according to claim 28, wherein the flow flangeassembly comprises an upper flow guide connected to a main flange body,wherein a first fluid gap is positioned between the upper flow guide andthe main flange body.
 32. The chemical vapor deposition reactoraccording to claim 31, wherein a second gap located between the outwardfacing surface of the wafer carrier and an upper surface of the upperflow guide is about 1 inch or less.
 33. The chemical vapor depositionreactor according to claim 28, wherein the upper shaft segment isfabricated from a material having a lower thermal conductivity thanremaining segments of the center rotation shaft.
 34. The chemical vapordeposition reactor according to claim 28, further comprising: a radiantheat source.
 35. The chemical vapor deposition reactor according toclaim 28, further comprising: a reactor, wherein the center rotationshaft has two or more segments that are used in the reactor.
 36. Thechemical vapor deposition reactor according to claim 28, wherein thecenter rotation shaft extends downward from a center of a bottom surfaceof the wafer carrier.
 37. The chemical vapor deposition reactoraccording to claim 28, wherein the center rotation shaft comprises atleast two shaft segments made from different materials.
 38. The chemicalvapor deposition reactor according to claim 37, wherein the upper shaftsegment is made from graphite.
 39. The chemical vapor deposition reactorof claim 37, wherein a lower shaft segment of the center rotation shaftis made from sapphire.
 40. The chemical vapor deposition reactor ofclaim 28, wherein the center rotation shaft further comprises a lowershaft segment, wherein the at least one shaft segment, selected from theupper and lower shaft segments, has a substantially lower thermalconductivity than remaining shaft segments of the center rotation shaft.41. The chemical vapor deposition reactor of claim 40, wherein the uppershaft segment is fabricated from a high thermal conductivity materialand one or more of the remaining shaft segments of the center rotationshaft is fabricated from a material having a lower thermal conductivitythan the upper shaft segment.